Keywords: amination ate complexes carbomagnesiation carbometalation Grignard reagents homocoupling magnesates magnesium compounds metalation

Transcription

1 VII Abstracts 2010 p Aryl Grignard Reagents H. Yorimitsu Halogen magnesium exchange between aryl iodides or bromides and an isopropylmagnesium chloride lithium chloride complex or lithium trialkylmagnesates is now recognized as a useful method for the preparation of aryl Grignard reagents in addition to the conventional Grignard method. The exchange reactions lead to a wide variety of functionalized aryl Grignard reagents containing, for example, a carbonyl or a cyano group. Directed ortho-magnesiation reactions of arenes with bulky magnesium amide complexes, such as (2,2,6,6-tetramethylpiperidin-1-yl)magnesium chloride lithium chloride complex and bis(2,2,6,6-tetramethylpiperidin-1-yl)magnesium bis(lithium chloride) complex, are also useful. Ar 1 = I, Br iprmgcl LiCl Ar 1 MgCl LiCl Keywords: amination ate complexes carbomagnesiation carbometalation Grignard reagents homocoupling magnesates magnesium compounds metalation 2010 p Alkyl Grignard Reagents H. Yorimitsu While the conventional preparation of Grignard reagents from alkyl halides and metallic magnesium remains reliable, halogen magnesium and sulfoxide magnesium exchange have emerged as useful methods for the preparation of functionalized alkyl Grignard reagents that are otherwise difficult to synthesize. Carbomagnesiation reactions of alkenes are also useful for preparing alkyl Grignard reagents of some complexity. The formation of ate complexes gives a significant improvement in the utility of alkyl Grignard reagents and can lead to higher efficiency in nucleophilic addition to carbonyl compounds. R 2 Mg Mg = I, Br, SAr; R 2 = Et, ipr Keywords: ate complexes carbomagnesiation carbometalation cyclization magnesium compounds magnesates metalation Grignard reagents nucleophilic addition sulfoxides

2 VIII Science of Synthesis Abstracts 2010 p Magnesium Halides M. Shimizu This manuscript is an update to the earlier Science of Synthesis contribution describing reactions involving magnesium halides. It focuses on the literature published in the period In particular, magnesium bromide and magnesium iodide are used frequently as promoters for specific transformations of important molecules. R 2 + R 3 CH Mg 2, base H R 3 R 2 Keywords: Friedel Crafts reaction Knoevenagel reaction magnesium bromide magnesium chloride magnesium enolates magnesium fluoride magnesium iodide Morita Baylis Hillman reaction 2010 p Magnesium xide, Alkoxides, and Carboxylates M. Shimizu This manuscript is an update to the earlier Science of Synthesis contribution describing reactions involving magnesium oxide, alkoxides, and carboxylates. It focuses on the literature published in the period In particular, magnesium oxide and magnesium alkoxides are used for useful chemoselective transformations. TBDMS + MgBr R 2 R 3 THF H R 2 R 3 Keywords: Baeyer Villiger oxidation Diels Alder reaction ethyl magnesium malonate magnesium alkoxides magnesium bis[2-(alkoxycarbonyl)acetate] magnesium carboxylates magnesium monoperoxyphthalate magnesium oxide Mannich-type reaction Michael addition ppenauer oxidation 2010 p Product Subclass 14: Magnesium Amides M. Shimizu This manuscript is a revision of the earlier Science of Synthesis contribution describing reactions involving magnesium amides. Synthesis of a series of magnesium amides, bis- (amides), and their lithium chloride complexes is described. The use of magnesium amides as bases enables the regioselective deprotonation of a variety of molecules. Chiral magnesium amides are also discussed. Z H N MgCl LiCl Z MgCl LiCl E + Z E = C 2 R, CN, CR Z = directing group

3 Abstracts I Keywords: amidomagnesium halide lithium chloride complexes amidomagnesium halides magnesium bis(amide) lithium chloride complexes magnesium bis(amides) magnesium dialkylamides deprotonation 2010 p xazoles A. Khartulyari and M. E. Maier This manuscript is an update to the earlier Science of Synthesis contribution describing methods for the synthesis of oxazoles. This heterocyclic system is of particular interest, since many oxazole-containing natural products and their synthetic analogues possess interesting biological activities. In addition, oxazoles and related compounds serve as building blocks and reagents for organic synthesis. iprmgcl LiCl Mg LiCl = I or Br Keywords: oxazoles cyclization multicomponent reaction gold catalysis heterocycles N-propargylamides cycloisomerization coupling reactions 2010 p Acyclic and Semicyclic / Acetals L. S. Fowler and A. Sutherland This manuscript is an update to the previous Science of Synthesis contribution describing methods for the synthesis of acyclic and semicyclic acetals. It focuses on the literature published in the period 2007 to mid mol% AuCl 3 MeH, rt, 2.5 h Pr i H C 2 Et 2. sat. aq NaHC 3 Pr i 87% Me C 2 Et Keywords: acyclic acetals semicyclic acetals aldehydes ketones trialkyl orthoformates enol ethers cycloaddition dehydration acetalization

4 Science of Synthesis Abstracts 2010 p ,3-Dioxetanes and 1,3-Dioxolanes D. Carbery This manuscript is an update to the earlier Science of Synthesis contribution describing methods for the synthesis of 1,3-dioxetanes and 1,3-dioxolanes. It focuses on the synthesis and synthetic applications of 1,3-dioxolanes covered in the literature over the period Me Me Me Me HC HC Me Me H H TsH, toluene, 24 h 60% HC Me Me Me Me Me Me Keywords: dioxolane carbonyls diols protecting groups deprotection 2010 p Spiroketals E. A. Anderson and B. Gockel This manuscript is an update to the earlier Science of Synthesis contribution describing methods for the synthesis of spiroketals. It focuses on the literature published in the period H H R 4 H + + R 5 NH 2 5 mol% [Pd(NCMe) 4 ](BF 4 ) 2 MeCN, rt, 2 12 h R 2 R 3 R 4 R 4 R 3 Mg(Cl 4 ) 2, HCl 4 CH 2 Cl 2 /MeCN, rt, 3 d R 2 R 3 R 2 NHR 5 NHR 5 Keywords: spiroketal acetalization benzannulation carbon -oxygen bonds cyclic compounds diastereoselectivity intramolecular reactions oxiranes oxygen heterocycles synthesis design spiro compounds

5 Abstracts I 2010 p Product Class 16: Glycosyl xygen Compounds (Di- and ligosaccharides) A. V. Demchenko and C. De Meo This manuscript is a revision of the earlier Science of Synthesis contribution describing methods for the synthesis of di- and oligosaccharides. Recent new developments and important improvements of fundamental concepts are the particular focus of this update. P LG + H P activator P P glycosyl donor glycosyl acceptor disaccharide conventional stepwise or expeditious assembly P P n oligosaccharides LG = leaving group; P = protecting group Keywords: carbohydrates enzyme catalysis glycosidases glycosidation glycosides glycosylation halides imidates neighboring-group participation neuraminic acids nucleophilic substitution oligosaccharides protecting groups solid-phase synthesis saccharides stereoselective synthesis sugars thioglycosides thioimidates New p Product Class 17: Acyclic Hemiacetals, Lactols, and Carbonyl Hydrates S. C. Coote, L. H. S. Smith, and D. J. Procter Acyclic hemiacetals are in most cases unstable and exist only as transient intermediates, in contrast with cyclic hemiacetals (lactols), which are often stable, isolable compounds. Lactols may be prepared using various different methods, including the reduction of lactones, reduction of dicarbonyl compounds, or the selective oxidation of diols, as well as by addition of carbon nucleophiles to lactones or dicarbonyl compounds, deprotection of -protected cyclic hemiacetals, or from enol ethers. Carbonyl hydrates are generally short-lived intermediates, although a limited number of stable carbonyl hydrates (generally derived from strained carbonyl compounds or carbonyl compounds bearing electron-withdrawing groups) have been documented. H n H n Keywords: carbonyl additions carbonyl compounds dicarbonyl compounds diols hydroxycarbonyl compounds lactols lactonization oxidation reduction

6 II Science of Synthesis Abstracts New p Product Class 18: 1,1-Diacyloxy Compounds L. H. S. Smith, S. C. Coote, and D. J. Procter 1,1-Diacyloxy compounds can be accessed from a variety of starting materials including aldehydes, ketones, and /, /Hal, and Hal/Hal acetals under a variety of reaction conditions. This product class encompasses Meldrum s acid, several natural products, and acyloxy ester prodrugs; in addition, acyl acetals are useful protecting groups for aldehydes and can be cleaved orthogonally to alkyl acetals. H H + R 2 R3 R 4 H + R 2 R 3 R 4 Keywords: acetals acylation alkylation carbonyl compounds carboxylic acids esters Lewis acid catalysts oxidation